1. Field of Invention
The present invention relates to a system and method for drilling soft tissue and positioning an intramedullary rod in a long bone.
2. Description of the Related Art
Intramedullary rods are commonly used in orthopedic surgery for breaks in the long bones of the extremities, such as the femur and tibia. These rods are used to align and stabilize fractures or breaks of bones and to maintain the bone fragments in their proper alignment relative to each other during the healing process. In addition, intramedullary rods can provide strength to the bone during the convalescence of the patient. One common surgical rod implantation procedure involves drilling the bone marrow canal of the fractured bone from a proximal to a distal end of the bone and inserting an intramedullary rod into this evacuated space. In order to maintain the intramedullary rod in the proper relationship relative to the bone fragments, it is often desirable to insert bone screws or other fasteners through the distal and proximal portions of the intramedullary rod and one or both fragments of the bone. Such a fixation of the rod can make the construct more stable, prevent rotation of the rod within the bone, and prevent longitudinal movement of the bone relative to intramedullary rod.
In order to fix the rod to the bone, intramedullary rods are commonly provided with at least one hole through each of their proximal and distal end portions for receiving screws or fasteners of various configurations. To insert such screws, the objective is to drill holes through the tissue and bone in proper alignment with the holes in the intramedullary rod, and to insert the screws through the holes to lock intramedullary rod in place. Locking the rod near its proximal end (near its point of insertion) is usually accomplished with the help of a jig that helps to locate the proximal hole(s) in the rod. In this proximal region, a relatively short-aimed aiming device can be attached to the jig for reference. A drill can then be passed through the bone and a proximal hole. This technique is relatively straightforward due to the short distance between the accessible proximal end of the rod and the proximal holes in the rod. However, due to the distance between the proximal end of the rod and the point where the holes must be drilled in the bone at the distal end of the rod, it can be difficult to register the drilled hole(s) with the holes in the distal end of the rod. This is particularly true in cases where rod deformation occurred during insertion of the rod into the intramedullary cavity. It can therefore be difficult to successfully align transverse screws with the distal hole(s) for insertion through the bone wall.
Particularly, it is known to those of ordinary skill in the art that an intramedullary rod has a general tendency to bend in the anterior-posterior direction during insertion into the bone, particularly in the femur. The anterior-posterior direction is perpendicular to the axis of the distal rod hole, and thus significantly affects the alignment between the drill-guiding hole in the aiming device and the distal hole in the rod. Medial-lateral bending on the other hand does not significantly affect drill-guiding alignment with the distal hole since the medial-lateral direction is parallel to the axis of the distal hole. Because there is no guarantee that the rod will not bend during insertion, there is always a possibility of misalignment between the distal screw hole and the drill-guiding hole, even assuming perfect alignment between the distal rod hole and the drill-guiding hole prior to nail insertion.
Two primary reasons for failure in distal locking of intramedullary rod to the bone include using an incorrect entry point on the bone and having the wrong orientation of the drill. If either of these two factors exists, the drill may not go through the hole in the rod. An inaccurate entry point also compounds the problem if the rounded end of the drill bit is slightly out of position, thereby weakening the bone and sometimes making it difficult to find a strong point in the bone in which to place the correct drill hole. Inaccurate distal locking can lead to premature failure with breakage of the rod, breakage of the screw, or the breaking of the drill bit within the bone. In addition, if the distal end of the rod is not properly secured, bone misalignment and/or improper healing of the bone may occur.
One known technique for locating a distal hole in an intramedullary rod is with x-ray imaging in combination with a free hand drilling technique. This technique involves watching a fluoroscopic image intensifier to accomplish distal targeting. However, this technique is difficult to use and adds the additional risk of exposing the patient and surgical team to excessive radiation. Even if protective gloves and clothing are utilized, there can still be risks involved with radiation exposure. This can particularly occur in cases where locating the hole(s) in the rod requires multiple attempts. In addition, if the correct alignment of the components is not obtained on the first attempt, multiple perforations of the bone can be required, which can be detrimental to recovery of the patient and the strength of the bone in this area.
Alternative techniques for locating the distal holes in an implanted intramedullary rod have been proposed. However, such methods are often relatively complex and can require additional electronic equipment and visual displays for operation. Such techniques may require special training and/or machine operators, and can be relatively expensive. These techniques can thus be undesirable in the crowded space of a surgical suite, particularly when it is desirable to minimize the amount of equipment and personnel involved in the surgery. Thus, there is a continued need for surgical drilling tools, devices and methods that allow a surgeon to accurately locating the distal holes in an implanted intramedullary rod and for drilling through these holes to allow the rod to be securely fastened to the bone.